Circuit-opening device for interrupting heavy currents by means of an explosive charge

ABSTRACT

A circuit-opening device comprising an explosive circuit-breaker which consists of a hollow conductor housing an explosive cartridge, an explosive charge and a detonator and also an operating current relay in the form of, say, a low-voltage spark gap, a trigatron or thyratron, the place where the electric circuit is opened being in the form of two parallel branches, one of which includes only an explosive circuit-breaker and serves continuously to carry the operating current while the other branch includes an explosive circuit-breaker and a seriesconnected operating current relay, which normally does not pass the operating current.

llnited States Patent 1191 Kozorezov et a1.

[ Nov. 26, 1974 CIRCUIT-OPENING DEVICE FOR INTERRUPTING HEAVY CURRENTS BY MEANS OF AN EXPLOSIVE CHARGE [76] Inventors: Konstantin Isaakovich Kozorezov,

Universitetsky prospekt 21, korpus, 1, kv. 29; Vitaly Vasilievich Semchenko, ulitsa 26 Bakinskikh Komissarov, 8, korpus 3, kv. 32; Georgy Ivanovich Mikhailu, ulitsa Volgina 23, korpus 1, kv. 52, all of Moscow, U.S.S.R.

22 Filed: Dec.26, 1973 21 Appl. No.: 428,901

[52] US. Cl 317/40 A, 337/30, 337/293, 337/401 [51] Int. Cl. H01h 39/00, H02h 5/00 [58] Field of Search 337/30, 290, 293, 243, 337/401, 161; 317/66, 40 A, 15

[56] References Cited UNITED STATES PATENTS 12/1942 McMorris 337/30 9/1953 Kozalka 337/293 X 2,892,062 6/1959 Bruckner et a1, 337/290 3,155,797 11/1964 .lanes 337/293 3,296,518 l/1967 Stumpe... 317/40 A X 3,400,301 9/1968 Misare 337/30 X 3,544,843 12/1970 Sletten et a1. 337/401 X Primary Examiner-A. T. Grimley Attorney, Agent, or Firm-Waters, Roditi, Schwartz & Nissen [57] ABSTRACT 2 Claims, 4 Drawing Figures CIRCUIT-OPENING DEVICE FOR INTERRUPTING HEAVY CURRENTS BY MEANS OF AN EXPLOSIVE CHARGE The present invention relates to electric engineering more particularly to explosive circuit-breakers and can be used for quick interruption of electric circuits carrying currents above 1,000 A at a voltage above 1,000 V.

The invention can be used with maximum efficiency in the circuits of inductive and capacitive storage devices. In these circuits a distinction must be made between the full opening time, 7;, measured from the instant when a control signal is produced to the instant when the current is interrupted, and the intrinsic opening time, 1,, measured from the beginning to the end of circuit interruption.

The circuit of, say, an inductive storage device consists of a series combination of a current source, a storage device and a circuit-opening device connected in parallel with the load. During storage of the current, which lasts from several fractions of a second to hundreds of seconds, the load remains shunted by the circuit-opening device and no energy is liberated in the load. During the time that elapses from the instant when a control signal is produced to the beginning of circuit interruption (Tr-13) again no energy is liberated in the load and this time period is not essential as it can always be allowed for. Finally, during the intrinsic opening time, 7,, the current of the storage device is redistributed to the load, though part of the energy is liberated in the circuit-opening device, affecting its efficiency.

Apart from high speed of operation the circuitopening device must possess a high degree of reliability as incomplete interruption may result in a considerable amount of energy being liberated in the device causing various emergencies.

This last consideration as well as the efforts to minimize the intrinsic opening time, 1",, prompted the use of explosives in circuit-opening devices.

There exist explosive circuit-breakers disclosed in FRG Pat. No. l,2933l3, class 2lc-69 and U.S. Pat. No. 2892062 class 337-290. These devices include a tubular conductor housing an explosive charge. The charge is activated by a detonator. The narrow middle or end section of the conductor has longitudinal slits, lateral notches and solder joints. The tubular conductor is connected in parallel with a lowinductance fuse comprising two bifillar-wound coaxial conductors.

When the explosive charge is activated, the hollow conductor breaks and goes apart fanwise, while the ends of the conductor serve as nozzles through which the arc produced by the break-induced currents is extinguished by the explosion products. The are voltage rises to a value at which the current is switched to the fuse. The circuit is completely interrupted when the fuse links melt.

However, whatever the construction of the conductor broken by the explosion the velocities of its fragments and, consequently, the arc extinction time and the intrinsic opening time are largely dependent on the charge coefficient, 7 the ratio of the mass of the explosive to the mass of the conductor. The fact that the conductor has to carry the full storage current necessitates an increase in the mass of the conductor, the mass of the explosive and the mass of the structures which localize the explosion. Lastly, part of the stored energy is consumed for blowing the fuse, reducing the efficiency of the storage device.

The present invention aims at obviating the above disadvantages and at providing a device which possesses a high degree of reliability, has an operating speed of 1-5 microsecs and requires a limited quantity of the explosive.

We hereby disclose a circuit-opening device for interrupting heavy currents by means of an explosive charge wherein the place where the circuit is opened is in the form of two parallel branches, according to the invention, the first branch includes only an explosive circuit-breaker and the second branch includes a series combination of an explosive circuit-breaker and an operating current relay, so that, when the circuit is being opened, the first branch is interrupted first, the current is transferred to the second branch and then the second branch is interrupted after a time delay sufficiently long to allow the circuit-breaker of the first branch to form a gap capable of withstanding all subsequent voltage surges.

In accordance with the invention the circuit-opening device is provided with two explosive circuit-breakers of existing design, connected in parallel, so that one of said circuit-breakers, referred to below as an operating current circuit-breaker, has a large cross-sectional area, a small specific charge and is designed continuously to carry the operating current while the other of said circuit-breakers, referred to below as a peaking circuit-breaker, has a small cross-sectional area, a large specific charge and is designed to carry the operating current for short time periods. Connected in series with the peaking circuit-breaker is an operating current relay in the form of, say, low-voltage spark gap, thyratron, trigatron, etc., so that no current flows through the relay in the initial condition.

Both circuit-breakers can be exploded by means of comparatively small explosive charges and the conductors of the operating current circuit-breaker break within several milliseconds or more while the conductors of the peaking circuit-breaker break within 5 to 10 microsecs and less.

The invention makes it possible to avoid the use of large explosive charges and bulky and heavy protective housings which localize the explosion. For interruption of currents in high-voltage circuits the operating current explosive circuit-breakers as well as the peaking explosive circuit-breakers may be connected in series, each circuit breaker being designed for a low voltage rating. In this case there is no need to use only two explosive circuit-breakers with a high voltage rating. At such time steps must be taken to ensure highly simultaneous operation especially of peaking circuit-breakers.

For interruption of very heavy currents the operating current explosive circuit-breakers as well as the peaking explosive circuit-breakers may be connected in parallel, each circuit-breaker being designed for a low current rating.

These and other objects and advantages of the present invention will be better understood from the following description of the preferred embodiment thereof, when read in connection with the accompanying drawings, in which:

FIG. 1 shows a circuitopening device, according to the invention;

FlG. 2 is a time diagram which explains operation of the device;

FIG. 3 shows a multi-step circuit-opening device;

FIG. 4 shows another version of a circuit-opening device.

FIG. 1 shows a circuit-opening device which comprises two parallel branches 1 and 2 connected in an electric circuit 3, the branches 1 and 2 representing the circuit section which is exploded to open the circuit 3. The branch 1 contains an operating current explosive circuit-breaker 4 which consists of a hollow conductor 5 made of a material with a low density and high thermal and electric conductivity, such as magnesium or aluminium, and an explosive cartridge 6. The cartridge 6 contains an explosive charge (not shown) and can be electrically activated at any desired instant through the connecting wires by means of a switch which connects these wires to a current source. Such ignitors are well known in the art. The components of the explosive cartridge 6, the explosive charge, the ignitor and its control circuit are not shown in the drawings as they are not essential for describing the operating principle of the circuit-opening device.

. The branch 2 contains peaking explosive circuitbreaker 7 and an operating current relay 8 connected in series.

The peaking circuit-breaker 7 is identical in its construction to the operating current circuit-breaker 4 and its hollow conductor is made of a material which has a low density and high thermal and electric conductivity, preferably, magnesium or its alloys. The explosive charge contained in the cartridge of the peaking circuit-breaker may be electrically activated by means of connecting wires, a switch, and a current source not at any desired instant but with a certain time delay relative to the actuation of the operating current circuitbreaker 4. Such electric devices are well known in the art and can be applied in the given case.

The operating current relay 8 normally does not pass the operating current and is made in the form ofa lowvoltage spark gap, a trigatron or a similar device which are also well known in the art.

FIG. 2 shows a timing diagram which explains the operation of the circuit-opening device. In the normal condition the full operating current of the electric circuit 3 flows through the branch 1 as the branch 2 is disconnected by the operating current relay 8. Interruption of the current begins when the explosive charge of the cartridge 6 is ignited. The hollow conductor 5 breaks and the current is interrupted in the branch 1. This energizes the operating current relay 8 and causes the current I to flow through the branch 2 via the peaking switch 7. Then, after a time delay 1' provided by an electric delay means the explosive charge of the peaking circuit-breaker 7 is ignited. The time delay 'r is selected such as to enable the operating current circuitbreaker 4 to form a gap capable of withstanding all subsequent voltage surges in the electric circuit 3.

When the hollow conductor of the peaking switch 7 breaks, the electric circuit 3 is completely interrupted.

The device described above makes it possible to separate the functions performed by its various assemblies and attain the objects mentioned above: i.e., to reduce the intrinsic opening time 7,, decrease the total amount of the explosive and improve the reliability.

= h pcl where h length of the thin hollow conductor 5;

p density; 0 thermal capacity;

thermal conductivity. Under steady-state conditions (with t T tduration of the flow of the operating current T) the maximum temperature rise 0 is equal to 0, T h /8 0'8 with t 1' a where 0' electric conductivity;

S cross-sectional area of the hollow conductor 5,

the other symbols being the same as above. Under the transient conditions (with t the maximum temperature rise 0, is equal to:

0, Ft/pca-S At the same time it is well known that explosive charges possess a limited chemical stability and do not allow continuous heating, as the rate of the decompsition reaction increases 3.6-4 times with each 10C rise in temperature. Therefore there are practically no explosive charges which may be kept heated to temperatures above l00l20C for a long time (several minuts and more). Heating temperatures of 300C and somewhat higher are allowable for short time periods.

Analyzing the equation 2, which describes the conditions under which the existing circuit-breakers operate, it is obvious that the requirements of a small switching time, small explosive charge and a high reliability conflict with one another. A high reliability requires a large cross-sectional area of the circuit-breaker and a small switching time requires a large specific explosive charge.

However, in the device, according to the invention, use is made of two circuit-breakers and through the operating current circuibbreaker 4 operates under steady-state temperature conditions and is described by the equation 2 it must not necessarily have a high speed of operation. Besides, when the hollow conductor 5 breaks, the voltage across the operating current circuitbreaker 4 slightly rises, causing operation of the operating current relay 8. As a result the operating current circuit-breaker 4 is shunted by a low-resistance circuit and no special steps have to be taken in the circuitbreaker for are extinction. The size of the explosive charge 6 in this circuit-breaker may be considerably reduced and its construction may be simplified.

After the operating current relay 8 operates the branch 2 is connected and the current flows through the peaking switch 7. However, if the characteristics of this circuit-breaker are selected such that the time delay is less than the temperature transient time '(1' 7 o the temperature conditions are described by the euqation 1, from which it follows that even for a small cross-sectional area S heating can be minimized due to short duration t of the current flow.

Therefore in the device, according to the invention, each of the circuit-breakers performs separate functions: the operating current circuit-breaker 4 is designed for continuously and reliably carrying the operating current, while the peaking circuit-breaker 7 is normally disconnected by the operating current relay 8 and is used to reduce the intrinsic opening time. It has been found that the use of the device, according to the invention, saves up to 80 percent of the explosive charge as compared with explosive circuit-breakers of existing designs having the same operating speed.

FIG. 3 shows a multi-step circuit-opening device. This device comprises two parallel-connected branches 1 and 2 of the electric circuit 3. The'branch I has several operating current circuit-breakers 4 connected in series, the branch 2, several peaking circuit-breakers 7 and the operating current relay 8.

Such series connections are known in the techniques of current interruption at high voltages and prove to be quite suitable for use in the device described herein. Referring to FIG. 3, a multi-step circuitopening device comprises several standard circuit-breakers 4 and 7, each of which has a definite voltage and current rating and serves to interrupt currents at very high voltages. This enables reduction in the length h of the hollow conductor 5, and sections 9 which appear at the end faces of the operating current circuit-breaker 4 may be used for cooling each standard assembly (See Equation 2).

FIG. 4 shows another version of a circuit-opening device with parallel-connected operating current circuit breakers 4, peaking circuit-breakers 7 and the common operating current relay 8. Such arrangement of a circuit-opening device is preferably used very heavy currents.

In the case of very heavy currents at very high voltages use is made of parallel-connected groups of circuit-breakers, each group consisting of the seriesconnected operating current explosive circuit-breakers 4 and the peaking explosive circuit-breakers 7 provided with one common operating current relay 8. In this case as in the cases shown in FIG. 3 and FIG. 4 steps must be taken to ensure highly simultaneous ignition of the explosive charges, especially in the peaking circuitbreakers 7.

While the invention has been described above in reference to the preferred embodiment various modifications and changes may be made in the elements of the circuit-opening device without departing in any way from the spirit and scope of the present invention as claimed in the following claims.

What is claimed is:

1. A circuit-opening device for interrupting heavy currents by means of an explosive charge, wherein the place where a circuit is opened is in the form of two parallel branches, the first of which includes only an explosive circuit-breaker while the second branch includes a series-combination of an explosive circuitbreaker and an operating current relay, so that initially no current flows through the relay and, when the circuit is being opened, the first branch is interrupted first, the current is transferred to the second branch and then the second branch is interrupted after a time delay sufficiently long to allow the circuit-breaker of the first branch to form a gap capable of withstanding all subsequent circuit voltages.

2. A circuit-opening device as claimed in claim 1, wherein an operating current relay is made in the form of a low-voltage spark gap selected such that the gap breaks down when the first branch is interrupted.

for interrupting 

1. A circuit-opening device for interrupting heavy currents by means of an explosive charge, wherein the place where a circuit is opened is in the form of two parallel branches, the first of which includes only an explosive circuit-breaker while the second branch includes a series-combination of an explosive circuitbreaker and an operating current relay, so that initially no current flows through the relay and, when the circuit is being opened, the first branch is interrupted first, the current is transferred to the second branch and then the second branch is interrupted after a time delay sufficiently long to allow the circuit-breaker of the first branch to form a gap capable of withstanding all subsequent circuit voltages.
 2. A circuit-opening device as claimed in claim 1, wherein an operating current relay is made in the form of a low-voltage spark gap selected such that the gap breaks down when the first branch is interrupted. 